The refrigeration compressor is the heart of the automobile air conditioning refrigeration system. Its function is to maintain the circulation of refrigerant in the refrigeration system, suck in the low-temperature and low-pressure refrigerant vapor from the evaporator, compress the refrigerant vapor to increase its pressure and temperature, and send the refrigerant vapor to the condenser. Its principle is similar to that of ordinary air compressor, but the sealing degree is higher.
At present, the compressor used in automobile refrigeration system mainly adopts volumetric refrigeration compressor.
Scroll variable volume scroll swashplate compressor is an axial piston compressor, and its working principle is shown in the figure.
The main parts are spindle and inclined plate. Each cylinder is arranged with the main shaft of the compressor as the center, and the movement direction of the piston is parallel to the main shaft of the compressor.
The three cylinder swashplate is distributed with three pistons equally spaced at 120 °, and the five cylinder swashplate is distributed with five pistons equally spaced at 72 °. In order to make the machine bear reasonable force and compact structure, the piston is usually made into double headed piston. For example, the axial six cylinders, three cylinders are in the front of the compressor and the other three cylinders are in the rear of the compressor; In case of axial 10 cylinders, 5 cylinders are at the front of the compressor and the other 5 cylinders are at the rear of the compressor. The two pistons of the double headed piston are in the opposite cylinder (one front and one rear). When one end of the piston compresses the refrigerant vapor in the front cylinder, the other end of the piston sucks the refrigerant vapor in the rear cylinder and adjusts to each other in reverse. Each cylinder is equipped with high and low pressure air valves, and another high-pressure pipe is used to connect the front and rear high-pressure chambers. The inclined plate is fixed with the main shaft of the compressor, the edge of the inclined plate is installed in the groove in the middle of the piston, and the piston groove and the edge of the inclined plate are supported together through steel ball bearings.
When the main shaft rotates, the swashplate also rotates, and the edge of the swashplate pushes the piston to move back and forth axially. If the swashplate rotates for one cycle, the front and rear pistons complete a cycle of compression, exhaust, expansion and suction, which is equivalent to the action of two cylinders. In the case of axial 6-cylinder compressor, 3 cylinders and 3 double headed pistons are evenly distributed on the cylinder section. When the main shaft rotates for one cycle, it is equivalent to the function of 6 cylinders.
Rotary vane compressor the cylinder shape of rotary vane compressor has two shapes, one is circular and the other is oval.
There are 2-4 round cylinder blades and 4-5 oval cylinder blades. Rotary vane compressor has the largest cooling capacity per unit compressor mass. It has no piston and only one valve, called exhaust valve. The exhaust valve actually acts as a check valve to prevent refrigerant vapor from entering the compressor through the exhaust port when the cycle stops or the compressor is not running.
In the rotary vane compressor with circular cylinder, the impeller is installed eccentrically, and the outer circle of the impeller is close to the suction and exhaust holes on the inner surface of the cylinder. In a circular cylinder, the main shaft of the rotor coincides with the center of the ellipse, and the blades on the rotor and the contact line between them divide the cylinder into several spaces. When the main shaft drives the rotor to rotate for one cycle, the volume of these spaces changes in a cycle of “expansion reduction to almost zero”, and the refrigerant vapor also has a cycle of suction compression exhaust in these spaces. The compressed gas is discharged through the reed valve.
Rotary vane compressor has no suction valve, because the sliding blade can complete the task of suction and compression of refrigerant. For the circular cylinder, the two blades divide the space into two spaces, and the main shaft rotates for one cycle, that is, there are two exhaust processes; 4 blades have 4 times. The more blades, the smaller the discharge pulse of the compressor. For the oval cylinder, four blades divide the cylinder into four spaces, the main shaft rotates for one cycle, and there are four exhaust processes.